Presentation on theme: "Agenda 2/10 Warm-Up: Have you ever seen geologic problems in California on the news? What types of events make life more challenging on the West Coast?"— Presentation transcript:
1Agenda 2/10Warm-Up: Have you ever seen geologic problems in California on the news? What types of events make life more challenging on the West Coast?Soil Reading/WSMass Movement NotesMass Movement flipbook
3Mass MovementsMass movement: downslope movement of loose sediments and weathered rock resulting from the force of gravityAll occur on slopes; since very few places on Earth are flat, almost all Earth’s surface undergoes mass movementRange from extremely slow motionsto sudden slides, falls, and flowsMaterials moved: fine mud tolarge boulders
4Variables that influence Mass Movements: Material’s weight resulting from gravityMaterial’s resistance to sliding or flowing (friction between material and slope)Trigger: such as an earthquakeErosion and undermining of soil increase potential for earth’s materials to move downhill
5Other Variable: WaterToo little water: prevents sediment from holding together at allToo much water: can make slope unstable increasing weight of soils and sedimentIn this case: water not involved as transport agent; moves along with materials vs. materials moving along with water
6Types of Mass Movements: Creep Creep: slow, steady downhill flow of loose, weathered materials (soils)Move few cm per yearEffects seen over long periods of timeCan cause tilting of utility poles, fences, bending of trees, cracking of walls, breaking of underground pipelinesSolifluction: slow, downhill movement of loose, water-logged materials in regions of permafrost (mudlike liquid)
7Types of Mass Movement: Flows Flows: can move slowly as a few cm per year or hundreds of km per hourEarth flows: slow movements of soilMudflows: swiftly moving mixtures of mud and water triggered by earthquakes (common in volcanic regions and sloped semi-arid regions)Los Angeles Basin (southern CA) slopes left with little vegetation, heavy rains fall, cause mudflows
8Types of Mass Movement: Slides Landslide: rapid downslope movement of materials that occurs when thin block of soil, rock, and debris separates from underlying bedrock Rock Slide: type of landslide that occurs when sheet of rock moves downhill on sliding surface Very destructive form of mass movement!
9Types of Mass Movement: Slumps Slump: when mass material in landslide rotates and slides along a curved surfaceOccur in areas that have thick soils and on moderate to steep slopesCommon after rains because water reduces friction between grains of soil; weight of additional water pulls it downhillTriggered by earthquakes
10Types of Mass Movement: Avalanches Avalanches: landslides occur in mountainous areas with thick accumulations of snowUsually occur on slope10,000 avalanches each year in mountains of western USSun melts surface snow, then refreezes at night, snow falls on top builds up heavy, slip, slide down slope as avalanche
12Rock FallsOccur at high elevations, steep road cuts, on rocky shorelinesRocks loosened by physical weathering and plant growthRocks break up and fall downward
13Mass Movements Affect People Dangerous Mudflows: widespread loss of human life primarily result of location of villages both high up and in steep terrain and at foot of unstable, saturated slopesReducing the Risks: avoid building structures on such steep and unstable slopesTrenches used to divert water from a slope and control drainageCovering steep slopes with steel nets and protective fences
14Mass Movement flipbook Make a 6 flap foldable (like our Extreme Weather foldable). Each flap will have the name of one mass movement: Creep, Slump, Flow, Slide, AvalancheUse your notes/internet searches to fill in your foldableFront Flap: Title and Picture of the mass movementInside: definition, effects/trigger, what caused by, where these movements occur most often, and any other information you may want to add.